Sunday, October 28, 2012

(Update) The albacore tested after Fukushima had 340 – 1024 millibequerels/kg of combined cesium, according to Simplyinfo.org. 0.34 to 1.024 becquerels/kg. One-tenth of the bluefin tuna that the Stanford researchers tested.

(H/T anon reader)

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The Seattle Times article below doesn't report the number. It doesn't mention cesium-137 (half-life 30 years) either, which should have been detected alongside cesium-134 if it was of the Fukushima origin.

To avoid "baseless rumor", I suppose. But I still wish the reporter (or the researchers and government officials speaking to him) simply mentioned the number, instead of doing the "Edano" and saying "It's barely detectable, no effect on health, it's just so little ..."

The article says "it is allowing scientists to track the migratory patterns of tuna for the first time", which I take it to mean "the first time in Washington and Oregon". The researchers at Stanford University in California already announced the result of their study of bluefin tuna off southern California in May this year.

Researchers have found tiny amounts of radioactive cesium in albacore caught off Washington and Oregon. The radiation, originating from the 2011 tsunami in Japan, is thought to pose no public-health risk, but it is allowing scientists to track the migratory patterns of tuna for the first time.

Since the early 1950s, scientists have argued about one of the West Coast's most popular fish — albacore tuna.

Are the silvery streaks that tempt thousands of anglers each year part of one family of highly migratory fish? Or are there really two groups of speedy tuna, each traveling a different route around the sea?

Now this half-century-old argument could be clarified by a disturbing new pollutant: radioactive isotopes from Tokyo's Fukushima Daiichi nuclear power plant.

Oregon State University researchers and federal scientists are finding exceedingly tiny amounts of radioactive cesium in albacore caught off the coast of Washington and Oregon. And it's clear the radionuclide originated with the nuclear accident that followed the deadly tsunami that hit Japan in March 2011.

While some forms of cesium persist in the environment for decades, one isotope scientists saw, cesium-134, has a half-life of a little more than two years and could only have come from that accident.

So far, the trace amounts that OSU scientists found in tuna are far less than anything that would pose a risk to humans; a fish eater would have to consume several thousand pounds of the most radioactive albacore they discovered just to increase by 1 percent the amount of radiation they're exposed to from everyday sources.

"The amounts they found were incredibly small," said Donn Moyer, spokesman for the Washington state Department of Health, which also tested the same samples and came up with the same results. "There's nothing really remarkable about the amounts."

But because cesium decays so quickly, the discovery makes clear that fish caught in Northwest waters picked up the radiation while feeding on smaller fish in or around Japan.

"We're talking about barely, barely detectable levels," said Jason Phillips, who led the work while a graduate student at OSU's College of Earth, Ocean, and Atmospheric Sciences. "But because the radiation has to be derived from Fukushima, they had to pick it up within its vicinity or in the drift."

For most of the 1950s, researchers tagged North Pacific albacore and determined that the fish along the West Coast traveled between here, Japan and California and Mexico.

But in the 1970s researchers began to see signs that suggested some of the California fish might be part of a different population.

"It turns out there may be two different populations," said Richard Brodeur, with the National Marine Fisheries Service. "Ours up here might be completely different from those down off of California."

But the fast travel so far and fast — between 50 and 200 miles in a day — that tracking their movements is almost impossible, and no one has been able to confirm their theory.

After the Fukushima disaster, Phillips and Brodeur and another graduate student in radiation health had an idea: Why not map migration routes for West Coast tuna using the radioactive fish?

But the real test is yet to come. The scientists have been collecting dozens of albacore from fishermen off the California coast. They plan to test those fish soon. If those don't show the same traces of cesium-134, it would suggest that they didn't travel to the same place as the Northwest fish.

Understanding when and where albacore travel can help scientists protect stocks of a West Coast fish worth tens of millions of dollars annually.

The researchers are presenting their findings to a conference in Italy this weekend.

The Stanford researchers found 4 Bq/kg of cesium-134 (and 6.3 Bq/kg of cesium-137) in bluefin tuna off California, which do migrate. Yellowfin tuna don't, and I'm not aware of any testing or study of the radiation in yellowfin tuna.

Oregon State University's press release on October 24, 2012 is more detailed, but still no number mentioned. The press release does say the researcher detected cesium-137 also, and the fish they tested were caught last year and frozen:

The researchers first identified two Fukushima-linked isotopes – Cesium-137 (Cs-137) and Cesium-134 (Cs-134) – this July, in samples of fish caught and frozen in 2011.

In the OSU press release, the researcher Delvan Neville says they tested about 70 pounds (about 32 kilograms) of tuna, or 18 samples:

“This is what we've seen after testing about 70 pounds of tuna,” Neville said. “When you've run one or two samples, you can't really say much about the population you're testing yet. When you've run five or six, you could make some guesses. When you're up to, at this time, 18 samples and everything has fallen fairly neatly into two groups of results, you can start to make some predictions about that population.

15
comments:

Anonymous
said...

Wonder if they tested the blood..not the flesh of the fish..and no mention of other nuclides..One comment..the fact Cesium is shorter lived..it could be the salmon are eating smaller fish (squid or ??) that CAME from off Fukushima..which would shorten the tranportation cycle. Or the real scary thought..if just a trace NOW..what was it to begin with???

They very rarely give out hard contamination numbers in the US media it is always low or of no immediate danger to human health. The researchers and the media are probably scared that they will be sued by the fishing industry for damaging their business.

The article opens with "tiny amounts of radiation coming from 2011 tsunami".Since when does radiation come from tsunamis?A wording along the lines of "X Bq/kg of radioactive contamination coming from Fukushima npp" would have placed the Seattle Times article closer to journalism and farther from propaganda.Beppe

"Everyday sources", like holding a cell phone to your ear all day? Last I heard, a landmark court case ruled that those phones DO increase cancer risk (which is something I've known all along).

By comparing, they are basically trying to say "it's safe because you're already screwed from other things".

Also, justifying ingestion of nuclear meltdown radiation as "being less than receiving other radiation from everyday sources" sounds irrelevant to me. Don't all types of radiation affect the body differently and last for different amounts of time? Idiots.

But less funny is the fact that the radiation is widely distributed, practically ubiquitary now.Thus we seem to have a new level of "background radiation" now, probably originating from fallout.

And the sad thing is that potentially every single fish has the chance of being sort of a "mobile hotspot", depending what it ate and where it traveled.

There is no real "safety" when one of a hundred or a thousand fish is highly radioactive with tens of thousands of becquerels and the others "only" one to ten becquerels.It depends on whether the particular fish on your plate has been in Fukushima waters or or ate fish/sea plants/planktin coming from there.Remember, it is still very unclear how much radiation was/is being released via groundwater and seabed contamination at the Fuku site. Only the immediate vicinity seabed at the Fuku site has been grouted, so there is still a large area of contaminated seabed there.

Waving a counter over a container of fish for a few seconds won't detect such "hotspot fish". Finding out the real extent of the contamination risk would require testing thousands of fish individuums.

This makes eating some kind of Russian Roulette. If you are unlucky, a single fish meal might boost up your internal contamination to record levels.Bon appetit!

0.34 - 1.02 Bq/kg combined will be roughly:0.2-0.7 Bq/kg Cs-1370.1-0.4 Bq/kg Cs-137(According to Fuku water data released by TEPCO, current ratio is ca. 1.5 to 2.)I guess they emphasized Cs-134, because traces of Cs-137 from nuclear testing are still around...

If aliens attacked us, we'd spend a year trying to investigate whether they actually attacked us or not, then a few more years trying to determine if the damage was negligible or worth retaliating for.

Friend of mine linked me to this, I'm the lead health physicist for this research.

We did originally include numbers for both Cs-137 and Cs-134 to be put in the press release, but it was cut on the basis that it took too much text to explain what the numbers meant. And yes, those fish that had detectable Cs-134 also had elevated Cs-137 levels compared to the pre-Fukushima fish, while those without any Cs-134 have still been in the same range.

The pre-Fukushima fish we've run range from 0.132 to 0.269 Bq/kg of Cs-137 and no detected Cs-134, and all those post-Fushima without Cs-134 detectable have fallen within this range. The other post-Fukushima fish have had 0.275-0.735 Bq/kg of Cs-137 and 0.065-0.289 Bq/kg of Cs-134. The TEPCO ratio is for radiocesium released by the plant, which would over-predict the Cs-134:Cs-137 ratio since these fish also had trace Cs-137 contributions from weapons testing fallout. Dose conversion factors for ingesting these radionuclides are 740 Bq/mrem for Cs-137 and 512 Bq/mrem for Cs-134. If you live in the US your normal annual dose is about 300 mrem from natural sources, and another 300 mrem from medical exposures (x-rays, CTs, and the like).

We weren't concerned about being sued by fisheries with this release. Because most people don't realize just how pervasive natural radiation is (and see radiation and radioactivity as something that only happens at special places), we were rather nervous there might be an alarmist/sensationalist news response. Thankfully most of the coverage I was able to see kept the gist of it, though there were a few errors (like comparing microwave ovens to ionizing radiation).

We started processing fish this year, and our first Cs-134 positive was in July of this year. We wanted to make sure to verify our methods with other labs and get a larger sample size before going public with it. Plenty of folks were looking in 2011 (including a pilot study a member of our team ran last year), but their detection limits were much higher than ours mainly because they were checking for food safety purposes.

Different types of radiation (alpha, beta, gamma) have different biological effects and range in tissue, yes. And, yes, different chemicals stay in the body for different periods of time and go to different tissues, and that varies depending on the method of intake. Those dose conversions already include the differences in their biological half-lives and biological effects, and the absorbed fraction by the beta & gamma components released in their decay.

Cell phones and home microwaves are not a suitable comparison to your normal radiation dose or radiation from these radionuclides. We're talking about what is properly called "ionizing radiation" which locally deposits enough energy to result in heavy ionization (lots of freed electrons). Microwaves, infrared from your fireplace, FM radio stations emit 'radiation' but these are non-ionizing radiation...in the same way that visible light is also 'radiation'. The normal radiation dose we're referring to are from cosmic rays, cosmogenic and primordial radionuclides inside your body, external gamma ray sources, and (the biggest one) radon gas decaying while its inside your lungs.

Thank you, Mr. Neville, for the information. Do you plan to test bluefin caught this year?

As to your concern about "alarmist/sensationalist news response", unfortunately many outside Japan who have followed the Fukushima nuclear accident have long shunned the mainstream media (for the sheer lack of coverage) and listen more to experts who have been sounding dire alarms. For people who do not follow the news, it probably didn't matter in the slightest.

Bluefin aren't caught in our neck of the woods to my knowledge, but Dan Madigan's group (who published the previous paper on the bluefin Cs-134) may be.

We are testing a lot more albacore from this year though; to get at the migration patterns and stock structure we're going to need lots of data points with a good geographic range (something like 80-100 fish). We'll be doing much of that work in partnership with Madigan's group actually.

We're also testing just about every part of the pelagic food web in the Northern California Current we could get samples of this year so we can get some good transport models *before* the liquid release makes its way to our waters. I don't expect those to ever reach a point of concern for food safety, but numbers are better than guesses, and everyone has the right to make their own choices on what they consider to be levels of concern. Hopefully those models will also make it easier to regulate those kinds of releases on our side of the Pacific as well.

Mr. Neville, are you looking into the bioconcentration of radioactive materials? Other nuclides? Last year Japan's NHK enlisted the marine researchers and measured radioactivity of seawater, ocean soil, seaweeds, shellfish and fish off Fukushima. They found high concentration of cesium and radioactive silver (Ag-110m) in shellfish (abalone) and fish, even when the environment had low levels of these nuclides. In fact, Ag-110m in water was non-detectable level. http://ex-skf.blogspot.com/2011/11/radioactive-ocean-nhk-survey-shows-174.html

Yes, I'm using gamma spectroscopy for quantifying the radiocesium, and the detector in question has a decent response for energies above about 60 keV. Ag-110m was one I was really interested to look for, especially in the 2011 samples, since silver tends to concentrate in fish tissue even higher than it does for cesium. No Ag-110m detected yet though. If its a gamma emitter and has a decent yield (e.g. usually emits said gamma when it decays) our analysis can detect it down to around 50mBq/kg. Lower energy (down to about 80-100 keV) I'll be able to detect even smaller concentrations, slightly higher limits for the higher energy ones.

I'll also be doing some chemical work to look for Sr-90 and Pb-210. The first is generally kept in the bone, though I will still be testing the edible muscle as well, and like Cs-137 is present from old fallout and may have been released by the Fukushima accident. You can't survey for it with a flyover like the gamma emission maps you might have seen though since it only emits a beta during its decay. The methods to separate it chemically are either very time consuming or very expensive and only somewhat time consuming. Pb-210 is a long-lived daughter of the radon decay chain, it has a low energy photon (40 keV) but is otherwise also just a beta emitter. It (and its daughters Bi-210 and Po-210) are going to be big sources of the normal dose to these fish, and I intend to be able to quantify not just what dose the fish are getting from Fukushima, but how that compares to the annual dose their population has been sustaining itself by over the last several decades.

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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